1. Field of the Invention
The present invention generally relates to a method and apparatus for testing trees. More particularly, the present invention is directed to a method and apparatus for selecting trees for harvest by testing the material properties of the trees in the field.
2. Description of the Related Art
It is known that it is necessary for lumber companies to test trees in order to determine which ones are to be cut down. For example, mature trees are selected for harvesting, while immature trees are left standing for further growth. One way to accomplish this is by taking a core sample of the tree and sending it to a laboratory to determine the density of the wood, which is related to the maturity of the tree. However, this process in undesirable because it is slow and injures the tree as coring typically produces a hole of from 1 to 3 inches in diameter which extends to the center of the tree. An opening of this size in the tree left by the coring process can provide an entryway into the interior of the tree for tree pathogens such as bacteria, fungi, and insect pests that ultimately cause the tree to rot.
Various methods for testing the material properties of trees in the field are known. For example, U.S. Pat. No. 3,877,294 to Shaw discloses a vibration technique for rot detection in wooden poles and trees. The technique includes applying a mechanical vibrational force at sonic frequencies to, for example, a pole to be tested for rot, and measuring the level of energy emerging from a number of axially spaced points along the length of the pole and comparing the measurements of the emergent energy at the respective points. Shaw teaches that decay induced rot manifests itself as a material of lower density than good quality wood. The less dense material presents a lower impedance and, for a given resonant-like input signal, emergent energy is higher than that passing through good wood.
What is needed, however, is a simple and inexpensive method for determining tree maturity in the field.
A method for selecting trees in accordance with a predetermined criterion is provided herein. In one embodiment of the present invention, a method for selecting trees is provided comprising applying a vibrative member to the tree, the vibrative member being characterized by mechanical vibration resonance properties; vibrating the vibrative member; determining the resonance properties of the vibrative member; calculating an observed quality factor associated with the vibrative member vibrations; and, comparing the observed quality factor with a predetermined relationship between the quality factor and the tree selection criterion.
Another embodiment of the present invention is a portable tree probe, suitable for field use, comprising (a) a vibrative member having a wood-penetrating end portion with at least one mechanical resonance frequency; (b) means for vibrating the vibrative member at about the resonance frequency of the wood-penetrating end portion; and, (c) means for measuring vibration amplitude across a frequency range sufficient to determine a characteristic Q value.
The method and portable tree probe of the present invention advantageously provide a way for trees to be tested in order to determine if a tree should be harvested, based on its maturity, with minimal damage to the tree. Thus, trees that are not cut down can remain standing for further growth and maturity without suffering from such problems as rotting.